Precision, Very Low Noise, Low Input
Bias Current Operational Amplifiers
AD8671/AD8672/AD8674
PIN CONFIGURATIONS
PLL filters
Filters for GPS
Instrumentation
Sensors and controls
Professional quality audio
NC
NC 1
7
V+
–IN 2
V+
TOP VIEW
6 OUT
(Not to Scale)
V– 4
5 NC
NC = NO CONNECT
Figure 1. 8-Lead SOIC_N (R-8)
OUT A 1
AD8672
8
V+
7
OUT B
TOP VIEW
6 –IN B
(Not to Scale)
5 +IN B
V– 4
+IN A 3
Figure 2. 8-Lead MSOP (RM-8)
OUT A 1
–IN A 2
Figure 3. 8-Lead SOIC-N (R-8)
OUT A 1
+IN A 3
8
AD8672
OUT B
TOP VIEW
6 –IN B
(Not to Scale)
5 +IN B
V– 4
+IN A 3
OUT A 1
13 –IN D
–IN A 2
12 +IN D
+IN A 3
14 OUT D
13 –IN D
AD8674
TOP VIEW 11 V–
+IN B 5 (Not to Scale) 10 +IN C
9
–IN C
8
OUT C
Figure 5. 14-Lead SOIC_N (R-14)
03718-B-005
–IN B 6
OUT B 7
12 +IN D
TOP VIEW 11 V–
+IN B 5 (Not to Scale) 10 +IN C
V+ 4
V+ 4
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The AD8671/AD8672/AD8674 are very high precision amplifiers
featuring very low noise, very low offset voltage and drift, low
input bias current, 10 MHz bandwidth, and low power
consumption. Outputs are stable with capacitive loads of over
1000 pF. Supply current is less than 3 mA per amplifier at 30 V.
V+
7
Figure 4. 8-Lead MSOP (RM-8)
14 OUT D
AD8674
NC
7
+IN 3
03718-B-001
NC = NO CONNECT
8
AD8671
03718-B-002
TOP VIEW
6 OUT
(Not to Scale)
V– 4
5 NC
–IN A 2
GENERAL DESCRIPTION
8
+IN 3
–IN A 2
APPLICATIONS
AD8671
–IN B 6
9
–IN C
OUT B 7
8
OUT C
Figure 6. 14-Lead TSSOP (RU-14)
The AD8671/AD8672/AD8674’s combination of ultralow noise,
high precision, speed, and stability is unmatched. The MSOP
version of the AD8671/AD8672 requires only half the board
space of comparable amplifiers.
Applications for these amplifiers include high quality PLL
filters, precision filters, medical and analytical instrumentation,
precision power supply controls, ATE, data acquisition, and
precision controls as well as professional quality audio.
The AD8671/AD8672/AD8674 are specified over the extended
industrial temperature range (–40°C to +125°C).
The AD8671/AD8672 are available in the 8-lead SOIC and
8-lead MSOP packages. The AD8674 is available in 14-lead
SOIC and 14-lead TSSOP packages.
Surface-mount devices in MSOP packages are available in tape
and reel only.
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
03718-B-004
NC 1
–IN 2
03718-B-003
Very low noise: 2.8 nV/√Hz, 77 nV p-p
Wide bandwidth: 10 MHz
Low input bias current: 12 nA max
Low offset voltage: 75 μV max
High open-loop gain: 120 dB min
Low supply current: 3 mA per amplifier
Dual-supply operation: ±5 V to ±15 V
Unity-gain stable
No phase reversal
03718-B-006
FEATURES
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
© 2005 Analog Devices, Inc. All rights reserved.
AD8671/AD8672/AD8674
TABLE OF CONTENTS
Specifications..................................................................................... 3
Total Noise vs. Source Resistance............................................. 11
Electrical Characteristics, ±5.0 V ............................................... 3
Total Harmonic Distortion (THD) and Noise ....................... 12
Electrical Characteristics, ±15 V ................................................ 4
Driving Capacitive Loads.......................................................... 12
Absolute Maximum Ratings............................................................ 5
GPS Receiver............................................................................... 13
ESD CAUTION ............................................................................ 5
Band-Pass Filter.......................................................................... 13
Typical Performance Characteristics ............................................. 6
PLL Synthesizers and Loop Filters ........................................... 13
Applications..................................................................................... 11
Outline Dimensions ....................................................................... 14
Unity-Gain Follower Applications ........................................... 11
Ordering Guide .......................................................................... 16
Output Phase Reversal............................................................... 11
REVISION HISTORY
6/05—Rev. B to Rev. C
Changes to Figure 6...................................................................... 1
Updated Outline Dimensions ................................................... 14
Changes to Ordering Guide ...................................................... 16
www.BDTIC.com/ADI
4/04—Rev. A to Rev. B
Changes to Figure 32.................................................................. 11
Changes to Figures 36, 37, and 38 ............................................ 12
1/04—Rev. 0 to Rev. A
Added AD8672 and AD8674 parts ..............................Universal
Changes to Specifications ............................................................ 3
Deleted Figure 3............................................................................ 6
Changes to Figures 7, 8, and 9 .................................................... 6
Changes to Figure 37.................................................................. 12
Added new Figure 32 ................................................................. 10
Rev. C | Page 2 of 16
AD8671/AD8672/AD8674
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS, ±5.0 V
VS = ±5.0 V, VCM = 0 V, TA = 25°C, unless otherwise noted.
Table 1.
Parameter
INPUT CHARACTERISTICS
Offset Voltage
Offset Voltage Drift
AD8671
AD8672/AD8674
Input Bias Current
Symbol
Conditions
VOS
∆VOS/∆T
–40°C < TA < +125°C
–40°C < TA < +125°C
IB
+25°C < TA < +125°C
–40°C < TA < +125°C
Input Offset Current
IOS
+25°C < TA < +125°C
–40°C < TA < +125°C
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Input Capacitance, Common Mode
Input Capacitance, Differential Mode
Input Resistance, Common Mode
Input Resistance, Differential Mode
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Output Voltage High
Output Voltage Low
Output Current
POWER SUPPLY
Power Supply Rejection Ratio
AD8671/AD8672
AD8674
Supply Current/Amplifier
Min
CMRR
AVO
CINCM
CINDM
RIN
RINDM
VCM = –2.5 V to +2.5 V
RL = 2 kΩ, VO = –3 V to +3 V
VOH
VOL
VOH
VOL
IOUT
RL = 2 kΩ, –40°C to +125°C
RL = 2 kΩ, –40°C to +125°C
RL = 600 Ω
RL = 600 Ω
PSRR
VS = ±4 V to ±18 V
–12
–20
–40
–12
–20
–40
–2.5
100
1000
Typ
Max
Unit
20
30
75
125
μV
μV
0.3
0.3
+3
+5
+8
+6
+6
+8
0.5
0.8
+12
+20
+40
+12
+20
+40
+2.5
μV/°C
μV/°C
nA
nA
nA
nA
nA
nA
V
dB
V/mV
pF
pF
GΩ
MΩ
120
6000
6.25
7.5
3.5
15
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DYNAMIC PERFORMANCE
Slew Rate
Settling Time
Gain Bandwidth Product
NOISE PERFORMANCE
Peak-to-Peak Noise
Voltage Noise Density
Current Noise Density
Channel Separation
AD8672/AD8674
+3.8
+3.7
110
106
+4.0
–3.9
+3.9
–3.8
±10
130
115
3
ISY
VO = 0 V
–40°C < TA < +125°C
SR
tS
RL = 2 kΩ
To 0.1% (4 V step, G = 1)
To 0.01% (4 V step, G = 1)
4
1.4
5.1
10
en p-p
en
in
0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
77
2.8
0.3
CS
f = 1 kHz
f = 10 kHz
–130
–105
GBP
Rev. C | Page 3 of 16
–3.8
–3.7
3.5
4.2
V
V
V
V
mA
dB
dB
mA
mA
V/μs
μs
μs
MHz
100
3.8
nV p-p
nV/√Hz
pA/√Hz
dB
dB
AD8671/AD8672/AD8674
ELECTRICAL CHARACTERISTICS, ±15 V
VS = ±15 V, VCM = 0 V, TA = 25°C, unless otherwise noted.
Table 2.
Parameter
INPUT CHARACTERISTICS
Offset Voltage
Offset Voltage Drift
AD8671
AD8672/AD8674
Input Bias Current
Symbol
Conditions
VOS
∆VOS/∆T
–40°C < TA < +125°C
–40°C < TA < +125°C
IB
+25°C < TA < +125°C
–40°C < TA < +125°C
Input Offset Current
IOS
+25°C < TA < +125°C
–40°C < TA < +125°C
Input Voltage Range
Common-Mode Rejection Ratio
Large Signal Voltage Gain
Input Capacitance, Common Mode
Input Capacitance, Differential Mode
Input Resistance, Common Mode
Input Resistance, Differential Mode
OUTPUT CHARACTERISTICS
Output Voltage High
Output Voltage Low
Output Voltage High
Output Voltage Low
Output Current
Short Circuit Current
POWER SUPPLY
Power Supply Rejection Ratio
AD8671/AD8672
AD8674
Supply Current/Amplifier
Min
CMRR
AVO
CINCM
CINDM
RIN
RINDM
VCM = –12 V to +12 V
RL = 2 kΩ, VO = –10 V to +10 V
–12
–20
–40
–12
–20
–40
–12
100
1000
Typ
Max
Unit
20
30
75
125
μV
μV
0.3
0.3
+3
+5
+8
+6
+6
+8
0.5
0.8
+12
+20
+40
+12
+20
+40
+12
μV/°C
μV/°C
nA
nA
nA
nA
nA
nA
V
dB
V/mV
pF
pF
GΩ
MΩ
120
6000
6.25
7.5
3.5
15
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DYNAMIC PERFORMANCE
Slew Rate
Settling Time
Gain Bandwidth Product
NOISE PERFORMANCE
Peak-to-Peak Noise
Voltage Noise Density
Current Noise Density
Channel Separation
AD8672/AD8674
VOH
VOL
VOH
VOL
IOUT
ISC
RL = 2 kΩ, –40°C to +125°C
RL = 2 kΩ, –40°C to +125°C
RL = 600 Ω
RL = 600 Ω
PSRR
VS = ±4 V to ±18 V
+13.2
+11
110
106
+13.8
–13.8
+12.3
–12.4
±20
±30
130
115
3
ISY
VO = 0 V
–40°C <TA < +125°C
SR
tS
RL = 2 kΩ
To 0.1% (10 V step, G = 1)
To 0.01% (10 V step, G = 1)
4
2.2
6.3
10
en p-p
en
in
0.1 Hz to 10 Hz
f = 1 kHz
f = 1 kHz
77
2.8
0.3
CS
f = 1 kHz
f = 10 kHz
–130
–105
GBP
Rev. C | Page 4 of 16
–13.2
–11
3.5
4.2
V
V
V
V
mA
mA
dB
dB
mA
mA
V/μs
μs
μs
MHz
100
3.8
nV p-p
nV/√Hz
pA/√Hz
dB
dB
AD8671/AD8672/AD8674
ABSOLUTE MAXIMUM RATINGS
Table 3. 1
Parameter
Supply Voltage
Input Voltage
Differential Input Voltage
Output Short-Circuit Duration
Storage Temperature Range
All Packages
Operating Temperature Range
All Packages
Junction Temperature Range
All Packages
Lead Temperature Range (Soldering, 60 sec)
1
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Rating
36 V
VS– to VS+
±0.7 V
Indefinite
–65°C to +150°C
–40°C to +125°C
–65°C to +150°C
300°C
Table 4. Package Characteristics
Package Type
8-Lead MSOP (RM)
8-Lead SOIC_N (R)
14-Lead SOIC_N (R)
14-Lead TSSOP (RU)
θJA 1
190
158
120
180
θJC
44
43
36
35
Unit
°C/W
°C/W
°C/W
°C/W
Absolute maximum ratings apply at 25°C, unless otherwise noted.
1
θJA is specified for the worst-case conditions, that is., θJA is specified for the
device soldered in circuit board for surface-mount packages.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
www.BDTIC.com/ADI
Rev. C | Page 5 of 16
AD8671/AD8672/AD8674
TYPICAL PERFORMANCE CHARACTERISTICS
45
32
35
24
20
16
12
8
30
25
20
15
10
4
0
10
20
30
40
50
60
FREQUENCY (Hz)
70
80
90
100
0
–35 –30 –25 –20 –15 –10 –5 0
Figure 7. Voltage Noise Density vs. Frequency
Figure 10. Input Offset Voltage Distribution
31.5
35
VS = ±15V
TA = 25°C
VS = ±15V
27.0
30
NUMBER OF AMPLIFIERS
22.5
25
www.BDTIC.com/ADI
18.0
13.5
9.0
20
15
10
4.5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
FREQUENCY (kHz)
03718-B-008
5
0
–35 –30 –25 –20 –15 –10 –5 0
5 10 15 20 25 30 35 40 45 50
VOS (μV)
03718-B-011
VOLTAGE NOISE DENSITY (nV/√Hz)
5 10 15 20 25 30 35 40 45
VOS (μV)
03718-B-010
5
03718-B-007
0
VS = ±5V
TA = 25°C
40
28
NUMBER OF AMPLIFIERS
VOLTAGE NOISE DENSITY (nV/√Hz)
VS = ±15V
Figure 11. Input Offset Voltage Distribution
Figure 8. Voltage Noise Density vs. Frequency
16
17.5
VS = ±15V
15
14
12.5
VOS (μV)
13
10.0
7.5
12
11
10
VS = ±5V
9
5.0
8
VS = ±15V
2.5
0
1
2
3
4
5
6
7
8
FREQUENCY (kHz)
9
10
6
–40
25
85
TEMPERATURE (°C)
Figure 12. Input Offset Voltage vs. Temperature
Figure 9. Voltage Noise Density vs. Frequency
Rev. C | Page 6 of 16
125
03718-B-012
0
7
03718-B-009
VOLTAGE NOISE DENSITY (nV/√Hz)
15.0
AD8671/AD8672/AD8674
14.5
5.0
VS = ±5V
14.0
4.0
13.5
OUTPUT VOLTAGE (V)
+IB
3.5
3.0
2.5
2.0
–IB
1.5
13.0
RL = 600Ω
12.5
12.0
11.5
11.0
1.0
10.5
0.5
25
85
125
TEMPERATURE (°C)
10.0
–40
03718-B-013
0
–40
25
85
03718-B-016
IB (nA)
VS = ±15V
RL = 2kΩ
4.5
125
TEMPERATURE (°C)
Figure 13. Input Bias Current vs. Temperature
Figure 16. Output Voltage High vs. Temperature
2.5
–11.0
VS = ±15V
VS = ±15V
2.0
–11.5
–IB
OUTPUT VOLTAGE (V)
1.0
–13.0
–13.5
25
85
125
TEMPERATURE (°C)
–14.5
–40
25
85
125
TEMPERATURE (°C)
Figure 14. Input Bias Current vs. Temperature
Figure 17. Output Voltage Low vs. Temperature
60
4.0
270
VSY = ±15V
RL = 10kΩ
CL = 20pF
ΦM = 59°
50
3.8
GAIN
40
OPEN-LOOP GAIN (dB)
3.6
3.4
3.2
3.0
VS = ±15V
225
180
135
30
90
20
PHASE
10
45
0
0
–10
–45
–20
–90
–30
–135
2.8
2.6
25
85
TEMPERATURE (°C)
125
03718-B-015
VS = ±5V
2.4
–40
03718-B-017
–1.0
–40
ISY (mA)
RL = 2kΩ
–14.0
03718-B-014
–0.5
RL = 600Ω
www.BDTIC.com/ADI
+IB
0
–12.5
–40
100k
–180
1M
FREQUENCY (Hz)
10M
Figure 18. Open-Loop Gain and Phase Shift vs. Frequency
Figure 15. Supply Current vs. Temperature
Rev. C | Page 7 of 16
OPEN-LOOP PHASE (dB)
0.5
–12.0
03718-B-018
IB (nA)
1.5
AD8671/AD8672/AD8674
30000
VSY = ±15V
VIN = 4V
RL = 2kΩ
±5V
VOLTAGE (1V/DIV)
25000
15000
±15V
10000
25
85
125
TEMPERATURE (°C)
03718-B-022
0
–40
03718-B-019
5000
TIME (100μs/DIV)
Figure 22. Large Signal Transient Response
Figure 19. Open-Loop Gain vs. Temperature
50
VSY = ±15V
VIN = 10mV
RL = ∞
CL = 20pF
AV = 100
20
AV = 10
VOLTAGE (50mV/DIV)
CLOSED-LOOP GAIN (dB)
30
VSY = ±15V
VIN = 200mV p-p
RL = 2kΩ
10
AV = 1
0
–10
–20
–30
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10k
1M
100k
10M
100M
FREQUENCY (Hz)
TIME (10μs/DIV)
Figure 23. Small Signal Transient Response
Figure 20. Closed-Loop Gain vs. Frequency
100
60
VS = ±15
SMALL SIGNAL OVERSHOOT (%)
90
80
70
60
50
AVO = 10
40
30
AVO = 100
AVO = 1
10
1k
10k
100k
1M
10M
FREQUENCY (Hz)
50
–OS
40
30
20
10
+OS
100M
03718-B-021
20
0
100
03718-B-023
–50
1k
03718-B-020
–40
Figure 21. Output Impedance vs. Frequency
0
100
1k
10k
CAPACITANCE (pF)
Figure 24. Small Signal Overshoot vs. Load Capacitance
Rev. C | Page 8 of 16
03718-B-024
40
IMPEDANCE (Ω)
AVO (V/mV)
20000
AD8671/AD8672/AD8674
160
VSY = ±15V
VOLTAGE (200mV/DIV)
VS = ±15V
VIN = 200mV p-p
AV = –100
RL = 10kΩ
140
120
0V
100
PSRR (dB)
VIN
VOUT
80
60
–PSRR
40
+PSRR
20
0
0V
TIME (4μs/DIV)
–40
10
100
1k
10k
100k
1M
03718-B-028
03718-B-025
–20
10M
FREQUENCY (Hz)
Figure 25. Positive Overdrive Recovery
Figure 28. PSRR vs. Frequency
135
VIN
VOLTAGE (200mV/DIV)
VS = ±2.5V TO ±18V
VSY = ±15V
VIN = 200mV p-p
AV = –100
RL = 10kΩ
134
133
PSRR (dB)
0V
132
131
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0V
130
VOUT
129
TIME (4μs/DIV)
127
–40
25
85
TEMPERATURE (°C)
Figure 26. Negative Overdrive Recovery
125
03718-B-029
03718-B-026
128
Figure 29. PSRR vs. Temperature
160
VSY = ±15V
VS = ±15V
140
VOLTAGE NOISE (50nV/DIV)
120
CMRR (dB)
100
80
60
40
20
100
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
03718-B-027
–40
10
TIME (1μs/DIV)
Figure 30. 0.1 Hz to 10 Hz Input Voltage Noise
Figure 27. CMRR vs. Frequency
Rev. C | Page 9 of 16
03718-B-030
0
–20
AD8671/AD8672/AD8674
0
VS = ±15V, ±5V
–40
–60
–80
–100
–120
–140
100
1k
1M
10k
100k
FREQUENCY (Hz)
10M
100M
03718-B-031
CHANNEL SEPARATION (dB)
–20
Figure 31. Channel Separation
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Rev. C | Page 10 of 16
AD8671/AD8672/AD8674
APPLICATIONS
UNITY-GAIN FOLLOWER APPLICATIONS
VSY = ±15V
When large transient pulses (>1 V) are applied at the positive
terminal of amplifiers (such as the OP27, LT1007, OPA227, and
AD8671) with back-to-back diodes at the input stage, the use of
a resistor in the feedback loop is recommended to avoid having
the amplifier load the signal generator. The feedback resistor,
RF, should be at least 500 Ω. However, if large values must be
used for RF, a small capacitor, CF, should be inserted in parallel
with RF to compensate for the pole introduced by the input
capacitance and RF.
VOLTAGE (1V/DIV)
VIN
03718-B-033
VOUT
Figure 32 shows the uncompensated output response with a
10 kΩ resistor in the feedback and the compensated response
with CF = 15 pF.
Figure 33. Output Phase Reversal
TOTAL NOISE VS. SOURCE RESISTANCE
OUTPUT UNCOMPENSATED
OUTPUT
COMPENSATED
The low input voltage noise of the AD8671/AD8672/AD8674
makes them a great choice for applications with low source
resistance. However, because they have low input current noise,
they can also be used in circuits with substantial source
resistance.
REF1 +OVER
23.23%
CH2 +OVER
7.885%
Figure 34 shows the voltage noise, current noise, thermal noise,
and total rms noise of the AD8671 as a function of the source
resistance.
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TIME (100ns/DIV)
03718-B-032
VOLTAGE (1V/DIV)
TIME (10μs/DIV)
For RS < 475 Ω, the input voltage noise, en, dominates.
For 475 Ω < RS < 412 kΩ, thermal noise dominates.
For RS > 412 kΩ, the input current noise dominates.
Figure 32. Transient Output Response
1000
C
100
in
10
en_t
(4kR ST)1/2
en
B
A
1
10
100
1k
10k
100k
SOURCE RESISTANCE (Ω)
Figure 34. Noise vs. Source Resistance
Rev. C | Page 11 of 16
1M
03718-B-034
Phase reversal is a change of polarity in the amplifier transfer
function that occurs when the input voltage exceeds the supply
voltage. The AD8671/AD8672/AD8674 do not exhibit phase
reversal even when the input voltage is 1 V beyond the supplies.
TOTAL NOISE (nV/√Hz)
OUTPUT PHASE REVERSAL
AD8671/AD8672/AD8674
TOTAL HARMONIC DISTORTION (THD) AND NOISE
0.1000
VSY = ±15V
RL = 2kΩ
CL = 1nF
VIN = 100mV
AV = +1
VOLTAGE (500mV/DIV)
The AD8671/AD8672/AD8674 exhibit low total harmonic
distortion (THD) over the entire audio frequency range. This
makes them suitable for applications with high closed-loop
gains, including audio applications. Figure 35 shows
approximately 0.0006% of THD + N in a positive unity gain, the
worst-case configuration for distortion.
CH2 +OVER
39.80%
CH2 –OVER
39.80%
03718-B-036
VS = ±5V
VIN = 2.5V
RL = 600Ω
0.0500
0.0200
TIME (10μs/DIV)
Figure 36. AD8671 Capacitive Load Drive
0.0050
RF
0.0020
LT1007
0.0010
0.0005
500Ω
RG
AD8671
500Ω
VCC
CF
220pF
0.0002
RS
50
100
200
500
1k
2k
5k
10k 20k
Hz
03718-B-035
0.0001
20
10Ω
CL
1nF
RL
2kΩ
VIN
VEE
Figure 35. Total Harmonic Distortion and Noise
03718-B-037
PERCENTAGE
0.0100
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Figure 37. Recommended Capacitive Load Circuit
DRIVING CAPACITIVE LOADS
The AD8671/AD8672/AD8674 can drive large capacitive loads
without causing instability. However, when configured in unity
gain, driving very large loads can cause unwanted ringing or
instability.
VOLTAGE (100mV/DIV)
CH2 –OVER
6.061%
TIME (10μs/DIV)
Figure 38. Compensated Load Drive
The output response of the circuit is shown in Figure 38.
Rev. C | Page 12 of 16
CH2 +OVER
5.051%
03718-B-038
Figure 36 shows the output of the AD8671 with a capacitive
load of 1 nF. If heavier loads are used in low closed-loop gain or
unity-gain configurations, it is recommended to use external
compensation as shown in the circuit in Figure 37. This
technique reduces the overshoot and prevents the op amp from
oscillation. The trade-off of this circuit is a reduction in output
swing. However, a great added benefit stems from the fact that
the input signal and the op amp’s noise are filtered, and thus the
overall output noise is kept to a minimum.
VSY = ±15V
RL = 2kΩ
CL = 1nF
CF = 220pF
VIN = 100mV
AV = +2
AD8671/AD8672/AD8674
ADC
LOW NOISE OP AMP
MIXER
VGA
AD8671
AD831
AD8671
DEMODULATOR
LOW-PASS FILTER
AD630
AD8610
AD10200
AD8369
03718-B-039
BAND-PASS FILTER
CODE GENERATOR
Figure 39. Simplified Block Diagram of a GPS Receiver
GPS RECEIVER
The band-pass response is shown in Figure 41.
GPS receivers require low noise to minimize RF effects. The
precision of the AD8671 makes it an excellent choice for such
applications. Its very low noise and wide bandwidth make it
suitable for band-pass and low-pass filters without the penalty
of high power consumption.
200μV/DIV
VS = ±15V
Figure 39 shows a simplified block diagram of a GPS receiver.
The next section details the design equations.
Filters are useful in many applications; for example, band-pass
filters are used in GPS systems, as discussed in the previous
section. Figure 40 shows a second-order band-pass KRC filter.
100
1k
10k
100k
10M
1M
www.BDTIC.com/ADI
R3
Hz
2.25kΩ
VCC
PLL SYNTHESIZERS AND LOOP FILTERS
C2
1nF
Phase-lock loop filters are used in AM/FM modulation.
1nF
R2
2.25kΩ
RB
18kΩ
RA
10kΩ
03718-B-040
VEE
Figure 40. Band-Pass KRC Filter
The equal component topology yields a center frequency
fo =
2
2πRC
and Q =
Loop filters in PLL design require accuracy and care in their
implementation. The AD8671/AD8672/AD8674 are ideal
candidates for such filter design; the low offset voltage and low
input bias current minimize the output error. In addition to the
excellent dc specifications, the AD8671/AD8672/AD8674 have
a unique performance at high frequencies; the high open-loop
gain and wide bandwidth allow the user to design a filter with a
high closed-loop gain if desirable. To optimize the filter design,
it is recommended to use small value resistors to minimize the
thermal noise. A simple example is shown in Figure 42.
2
4−K
PHASE
DETECTOR
where:
K =1+
R1
C1
10kΩ
VCC
1nF
CHARGE
PUMP
RB
RA
VCO
D
VEE
IN
Figure 42. PLL Filter Simplified Block Diagram
Rev. C | Page 13 of 16
03718-B-042
2.25kΩ
VIN
Figure 41. Band-Pass Response
C2
R1
03718-B-041
BAND-PASS FILTER
AD8671/AD8672/AD8674
OUTLINE DIMENSIONS
5.00 (0.1968)
4.80 (0.1890)
8
5
4.00 (0.1574)
3.80 (0.1497) 1
4
6.20 (0.2440)
5.80 (0.2284)
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
0.50 (0.0196)
× 45°
0.25 (0.0099)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
COPLANARITY
SEATING 0.31 (0.0122)
0.10
PLANE
8°
0.25 (0.0098) 0° 1.27 (0.0500)
0.40 (0.0157)
0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012-AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
Figure 43. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
3.00
BSC
8
3.00
BSC
5
4.90
BSC
www.BDTIC.com/ADI
1
4
PIN 1
0.65 BSC
1.10 MAX
0.15
0.00
0.38
0.22
COPLANARITY
0.10
0.23
0.08
8°
0°
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-187-AA
Figure 44. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
Rev. C | Page 14 of 16
0.80
0.60
0.40
AD8671/AD8672/AD8674
8.75 (0.3445)
8.55 (0.3366)
4.00 (0.1575)
3.80 (0.1496)
14
8
1
7
6.20 (0.2441)
5.80 (0.2283)
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0039)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
0.50 (0.0197)
× 45°
0.25 (0.0098)
1.75 (0.0689)
1.35 (0.0531)
SEATING
PLANE
8°
0.25 (0.0098) 0° 1.27 (0.0500)
0.40 (0.0157)
0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012-AB
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
Figure 45. 14-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-14)
Dimensions shown in millimeters and (inches)
5.10
5.00
4.90
14
8
www.BDTIC.com/ADI
4.50
4.40
4.30
6.40
BSC
1
7
PIN 1
1.05
1.00
0.80
0.65
BSC
1.20
MAX
0.15
0.05
0.30
0.19
0.20
0.09
SEATING
COPLANARITY
PLANE
0.10
8°
0°
COMPLIANT TO JEDEC STANDARDS MO-153-AB-1
Figure 46. 14-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-14)
Dimensions shown in millimeters
Rev. C | Page 15 of 16
0.75
0.60
0.45
AD8671/AD8672/AD8674
ORDERING GUIDE
Model
AD8671AR
AD8671AR-REEL
AD8671AR-REEL7
AD8671ARZ 1
AD8671ARZ-REEL1
AD8671ARZ-REEL71
AD8671ARM-R2
AD8671ARM-REEL
AD8671ARMZ-R21
AD8671ARMZ-REEL1
AD8672AR
AD8672AR-REEL
AD8672AR-REEL7
AD8672ARZ1
AD8672ARZ-REEL1
AD8672ARZ-REEL71
AD8672ARM-R2
AD8672ARM-REEL
AD8672ARMZ-R21
AD8672ARMZ-REEL1
AD8674AR
AD8674AR-REEL
AD8674AR-REEL7
AD8674ARZ1
AD8674ARZ-REEL1
AD8674ARZ-REEL71
AD8674ARU
AD8674ARU-REEL
AD8674ARUZ1
AD8674ARUZ-REEL1
Temperature Range
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Package Description
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
14-Lead SOIC_N
14-Lead SOIC_N
14-Lead SOIC_N
14-Lead SOIC_N
14-Lead SOIC_N
14-Lead SOIC_N
14-Lead TSSOP
14-Lead TSSOP
14-Lead TSSOP
14-Lead TSSOP
Package Option
R-8
R-8
R-8
R-8
R-8
R-8
RM-8
RM-8
RM-8
RM-8
R-8
R-8
R-8
R-8
R-8
R-8
RM-8
RM-8
RM-8
RM-8
R-14
R-14
R-14
R-14
R-14
R-14
RU-14
RU-14
RU-14
RU-14
Branding
BGA
BGA
A0V
A0V
BHA
BHA
A0W
A0W
www.BDTIC.com/ADI
1
Z = Pb-free part.
© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D03718–0–6/05(C)
Rev. C | Page 16 of 16